Part of Speech: Adjective
Meaning: 1. Related to the reappearance of a genetic trait or a behavior pattern after several generations of absence. 2. Reverting to an earlier, more primitive type, related to a throwback.
Notes: An atavism is a trait that reappears after several generations of absence (usually caused by a chance recombination of genes) or the process of reappearing itself. An atavist is an organism that reflects such a genetic trait—a throwback. A child's blue eyes may be an atavism if the trait does not occur in either parent but does occur in a grandparent or great-grandparent.
In Play: Atavism visits us where we least expect it. Sitting around a camp fire in the evening might be considered an atavistic pleasure, assuming our ancient ancestors did the same. If it is true that we spring from aquatic ancestors, splashing in the bathtub might be atavistic—or just fun. Could building tree houses and swinging on ropes be expressions of some deep-seated atavistic urge? But this word feels most comfortable in hyperboles, when throwback and primitive just don't say it all: "Andy Bellam is so atavistic, I'm surprised he doesn't drag Portia around by the hair."
Word History: This Good Word we traced from French atavisme (missed the "e"). It is made up of -isme added to the root of Latin atav-us "grandfather, ancestor", made up of ad "to(ward)" + av-us "grandfather." This makes atavistic a kinsword of avuncular "uncle-like", from Latin avunculus "maternal uncle" and, probably, English "abbot." The feminine variant of this word, avia "grandmother', seems to suggest that Roman grammas flew (they didn't). It did go on to become Portuguese aia "nursemaid," which Hindi borrowed as "aya" with the same meaning. (Today's Good Word flew in from the mind of the mysterious Gottsponer during a visit to the Alpha Agora.)

That Hindi got its āyā from Portuguese seems to be generally accepted.

Chinese āyí looks more problematic, as it has the meanings 1) (dial.) mother's sister, 2) a form of address for a woman of on's parents' generation, "auntie", 3) a nursemaid in a family or a childcare worker in a nursery school or kindergarten.

1 and 2 seem to indicate an old word, but when did meaning 3 come? A dictionary having its 1st ed. in 1943 lists only 1 and 2. So, perhaps Portuguese here as well?

Quite natural, I think. The ab or pa etc. father words like the ma mother words are found all over the world. (In some cases, the genders are inversed, making ma father and pa mother.) A theory to which I subscribe is that the very first sounds an infant makes are vowels plus labials, and parents more or less desperately interpret those combinations as referring to themselves.